Fan blade



"May 6 `1941` K c..v wHl'rEFlELD 2,240,597

FAN BLADE V A nieu June 1s, 1939 2 sheets-sheet 1 wlTNEssE-s: y' .Y

, INVENTQR .'/fy/e C. Whfe'e/d f BY ' ATTORNEY May 6, 1941# l( c. wHrrEl-IELD FAN BLADE Filed June 13, 1939 2 stunts-sheen 2 Fig] Fig.

ATTORNEY Patented May 6, 1941 UNITED STATES PATENT OFFICE Kyle C. Whitefield, Springiield, Mass., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 13, 1939, Serial 4No. 278,836;

4 claims. (ci. 17o-159) My invention relates to air-circulating fans, and it has particular relation to an improved de- 'sign of the blades, involving a new principle effecting an increase in the eiliciency of the fan, 4while at the same time securing, in general, a

reduction in the noise.

The principal object of my'invention is to proy a portion of the surface of the sphere or ellipsoid,

and with such a shape, as to provide the desirable features respecting the acceleration of air in a direction parallel to the axis ofthe fan, as will be subsequently described; while the double curvature of the sphere or ellipsoid, inthe axial direction, as well as in the peripheral direction, is ad vantageous in that the axial curvature may be utilized to offset the tendency of .the air to move radially away from the fan-blades under the operation of centrifugal force.

` My invention consists particularly in the bladeshapes, the fan-blade combinations, and the methods and systems, which are hereinafter described and claimed, and which are illustrated in the accompanying drawings, wherein:

Figure, 1 is a front elevational view of one-half of a single-piece sheet metal fan-blade structure having four blades, the major portion of the surl faces of which conform substantially to the surspider; the blade-surfaces in this case being of' ellipsoidal type. A

, In Figure 1, the fan-blades are'cut and stamped into shape, from a single .piece of sheet-metal, so

having a suitable radius R and a suitably located center, the center of the sphere for one of the blade-surfaces being indicated at 0 in Fig. 1.

At the portions of the fan-blade structure where the blades merge into the hub-portion. as indicated at I6, the approximately spherical curvature is modified, so as to blend the flat and curved surfaces together without sharp angles or bends. 'I'he direction of rotation of the fan is assumed to be counterclockwise as viewed :In Fig. 1, as indicated by lthe arrow. -Y

Each of the fan-blades II may .be regarded as having been cut from its spherical surface in such manner as to provide a forwardly curved leadingedge Il, extending ou-t from the hub I0; and ter-l as to provide a hub-portion I Il, and four blades II,` all of which are integrallyjoined together, with an annular strengthening-ridge or 'depression I2 in the hub-portion l0, and approximately radial, curved strengthening-ridges or depressions I3 extending ou-t into the respective blades II. Each of the blades I I is dished into a shape correspondlng substantially to the surface of a sphere 55 point I8 which is closer .to the fan-periphery I9 lthan to the hub I0, that is, the radius of the point I8 is morethan half of the radius of the periphery I9. As this forwardly projecting point I 8 extends the farthest forward.- around the surface. of the imaginary sphere from which the blade-surface is assumed (for purposes of description) to have been out, l'the blade-pitch in a peripheral direction is the smallest, at this point I8 in the leading edge Il, as indicated approximately'by the angle A in Fig. 4, although this cutting of a cylindrical cross-section through the blade I'I at the point I8, whereas Fig. 4 shows a cross-section cut by a plane surface which is indicated by the line IV--IV in Fig. 1. Itis desirable to have a minimum rate of acceleration of the air, in an axial direction, at this point I8 i the leading edge Ile-which is to say, that itis esirable to havea minimum fan-blade pitch, in a peripheraldirection, at this point I8 of the leading edge-because the peripheral speed is greater, here. than at other points in the leading edge which are closer to the hub-and since the peripheral speed is greater, a smaller entrance-angle or pitch of lthe blade is needed, in order to reduce the. noise produced by the air disturbance of the leading edge I l.

At portions beyond the region of the point I8, the ,leading edge {I'I curves baclrwardlyand merges gradually into the .fan-periphery I 8, so as to minimize disturbance of the air and to 'avoid going out 4too farforlwardly, on the com- Moving backwardly, along the fan-blade. from any point in the leading edge Il, and travelling along the intercept of a cylindrical surface on the blade-surface, that is, keepingat a constant radius from the fan-axis 2|, it willbe seen that the at points removed back from the leading edge I'l, so that, at the trailing edge 22, the air is given a strong forward acceleration inthe axial direc-r tion, so as to increase the Voutput of the fan, the,

trailing edge 22 being smoothly rounded off. so as to avoid excessive air-disturbance, which would result in noise.

The foregoing discussion 'considers thev moveblade-pitch, in this peripheral direction, increases ment of an air-particle as it travels peripherally across the surface of the. fan-blade, from the leading edge Il to the corresponding radial point in the trailing edge 22, during the rotation of the Y fan. vAs previously intimated, however, the airparticles are subjected also to centrifugal forces tending to move them out in la radial direction, and it is because of this centrifugal tendency that my blades are designed with a curvature in a radial direction as well as in a peripheral direc-.k

where the peripheral speed lis greater, andvit is most essential that the principles of my invention'be more carefully observed in the outer portion of the blade surface, than in the inner portions thereof, which arecloser to the center of rotation. I Tests have shown that my present invention effects a signicant increase in the eiciency of the fan, orfin the number of cubic feet of air, delivered by the fan, in proportion to the rate yof, power-consumption, or watts-energy required to drive the fan-blades. In general, also, my improved design results in a noticeable reduction in the noise of operation.

I claim as my invention:

, 1. A gas-circulating fan having a plurality, of blades, at least the outer half of each blade hav ing a surface which is substantially a predetermined portion of the surfaceof an ellipsoid, the

tion, so that the outer portions of the blades curve inwardly, so as to direct the air back or in, toward the axis of the fan. The center() of the spherical surface of the. illustrated blade fis,

located closely enough in, 'toward the axis of rotation, 2l, to provide the necessary rate of change of the blade-pitch in a radial direction y as well as in the peripheral direction.

The coordinates of the center 0 are indicated y at N and T in Fig. 1, and it will be seen that the center 0 is`disposed at a radius, from the axis 2l, which is less than the radius of the extreme forwardly projecting point I8 of the leading edge Il. The blade-pitch in aradial direction is substantially zeroat the radius of the center 0, and hence at a radius which is less than the radius of the point I8 at which the peripheral blade-pitch is a minimum. At radii longer tlianthe radius of the center 0, the blade-pitch in a radial direction increases on out-to the extreme peripheral edge I9, at which point the air is given a strong A impulse inwardly toward the axis, so as to operate in opposition to the centrifugal tendency of the air, due to the rotation o f the blades.

-While I have, thus far, specifically illustrated and explained my invention in relation to vbladesurfaceawhich are parts of spherical surfaces, or

surfacesof compound curvature' in which the Y rate of curvature is the same, or uniform, in two planes atvright angles to each other, it will lbe Yobvious that I am not limited to this uniformity of curvature. When the blades are being formed, or'dished out. it is obvious that they may be given any desired form of compound curvature, such vas is obtainable, in general, from any ellipsoidal type of surface. f v

In Figs. 6 and 7. I illustrate my invention, therefore, in a form utilizing blades '30 `having ellipsoidal surfaces, the general principles of the design being theY same, as already explained in In Figss 6 and 7. also, each blade 3l is separately formed,

connection with the spherical blades.

and is attached to a spider Ilfby any suitable means such as rivets 22, thus avoiding the limitations respecting the blade-pitch nearthe ceny ter of rotation,. where the integral blade-constructionshown'in Fig. l-'require'd a merged blade-and-hub surfacel I6. This spider-construction, .with separate. blades, Ythus Vpermits a very slight improvement in the blade-performance by improving the operation at points near the..center of rotation, but the most important portion of the blade isthe outerhalf thereof,

curvatures of each ellipsoid being such, and said predetermined portion thereof b`eing so shaped, and taken from such a part of the ellipsoid, that the blade-pitch in a peripheral direction is smallest at a point, in the leading edge, which is closer to the periphery than tothe axis of the fan, the blade-pitch in a peripheral direction' being larger at certain other leading-edge points than at said first-mentioned point, the blade-pitches in a peripheral direction increasing at points removed ba'ckvfrom the leading edge, the blade-pitch in a radial direction being substantially zero at a ray dius less than the radius of said first-mentioned point in the leading edge, and increasing at greater radii so as to operate in opposition to the centrifugal tendency of the gaseous medium in which the fan operates.

2'. A gas-circulating fan having four blades, at least the outer half of each blade having a surface whichvis substantially 'a predetermined por- -tion of the surface of an ellipsoid, the curvatures of each ellipsoid being such, and said predetermined portion thereof being so shaped, and taken Yfrom such a part of the ellipsoid, that the bladepitch in a peripheral/direction is smallest at a point in the leading edge, which is closer to the periphery than to the axis of the fan, the bladecentrifugal tendency of the gaseous medium in which the fan operates.

. 3. A gas-circulating fan having a plurality of blades. at least the outer half of each blade having a surface which is substantially a predeter- -mined portion of the surface of a sphere, said predetermined portion beingsoshaped,and taken from such apart of its sphere, that the blade-,

pitch vin a peripheral direction is smallest ata point, inthe leading edge, which is closer to the periphery than to the axis of the fan, the bladepitch in Va. peripheral direction being larger at vcertain other leading-edge points than at said first-mentioned point, theblade-pitches in a peripheral direction increasing at points removed back from the leading edge, the blade-pitch in a radialdirection being substantially zero at a radius less than the radius of said `first-mentioned point in the leading edge, and increasing at greater radii so as to operate in opposition to the centrifugal tendency of the gaseous medium in which the fan operates. f

4. A gas-circulating fan having four blades, a

least the outer half of each blade having a surface which is substantially a predetermined p0rtion of the surface. of a sphere, said predetermined portion being so shaped, and takeny from such a part of its sphere, that the blade-pitch in a peripheral direction is smallest at a point, in the leading edge, which is closer to the perpihery than to the axis of the fan, the blade-pitch in a 10 of the gaseous medium in which the fan operates.

n KYLE C. WHITEFIELD. 

